1a.Objectives (from AD-416):
The long-term objective of this project is to develop an improved understanding of how the changing cropping landscape impacts insecticide resistance development and management of various insect pest species in order to increase profitability and sustainability of mid-South row crops.

Objective 4: Improve low input systems of pest control for sweet potato by evaluating the efficacy and proper use of newly registered insecticides to enhance their integration with crop rotation and other low cost control strategies.

1b.Approach (from AD-416):
ARS scientists plan to improve tarnished plant bug control and insecticide resistance management by gaining new information on the pest’s ecology and biology using multi-disciplinary approaches. Analytical techniques, such as stable carbon isotope analysis, will be used to determine the influence of C4 host plants, such as field corn or pigweed, on populations of tarnished plant bug adults infesting cotton fields. This information will identify sources of tarnished plant bugs that may lead to alternative control measures prior to infestations into cotton fields. Tarnished plant bug populations will be monitored for resistance to various classes of insecticides commonly used by mid-South producers. This will provide real-time information to decision makers that will allow them to adjust their control recommendations based on the type of resistance that is found in their area of the mid-South. Detoxification enzyme activity surveys will be conducted in an effort to correlate and quantify insecticide resistance levels in field populations of the tarnished plant bug. Molecular genetics techniques will be conducted on tarnished plant bug populations that could lead to assays to evaluate the extent of field resistance in tarnished plant bug populations and provide input for insect management decisions. We also plan to determine the effect of bollworm ecology (corn earworm) on resistance to pyrethroid insecticides. Analytical techniques, such as stable carbon isotope analysis and a gossypol detection technique, will be used to determine the impact of bollworm larval plant host on pyrethroid resistance levels measured in adults collected from pheromone traps. Molecular genetics tools will be used to identify candidate genes and biological pathways associated with insecticide resistance in bollworm populations. Successful identification of loci associated with insecticide resistance and the development of genetic markers for those will provide a method to obtain quantitative estimates of field evolved resistance by estimating the allele frequencies via population studies. ARS scientists will also develop pest control strategies for the U.S. Mid-South’s Early Soybean Production System by determining accurate treatment thresholds and developing effective insecticide resistance management practices for the stink bug complex and bollworm. Field studies will be conducted to evaluate treatment thresholds for stink bugs and bollworms in early season soybeans. Stink bug populations will be monitored for potential resistance to various classes of insecticides, and this effort will provide real-time information to decision makers regarding the proper use of insecticides for control of these pests. ARS scientists also plan to improve low input systems of pest control for sweet potato by evaluating the efficacy and proper use of newly registered insecticides to enhance their integration with crop rotation and other low cost control strategies. Field and laboratory studies will be conducted to determine the impact of crop rotation on populations of insect pests of sweet potatoes, as well as information of insecticide efficacy and proper application techniques.

3.Progress Report:
For tarnished plant bug (TPB), contribution of pigweed and corn to adult populations within cotton fields can now be estimated using stable isotope analyses. Initial estimates indicate that ~80-90% of TPB adults collected from cotton fields in the Mississippi Delta during late June and early July completed nymphal development on a C4 host, primarily field corn. This may provide an opportunity to manage TPB populations prior to movement into cotton. Insecticide resistance monitoring in TPB populations indicated that control issues with acephate and pyrethroids will continue. TPB populations continue to be susceptible to thiamethoxam, imidacloprid, and novaluron. MS producers and consultants utilize this information when selecting insecticides for TPB control. TPB transcriptome sequence reads and their assemblies were made available to the public by depositing in the National Center for Biotechnology Information database. More than 200 xenobiotic processing gene transcripts were identified, and sequences were deposited in the database. Over 20,000 polymorphic genetic markers in expressed gene transcripts were also identified. Analysis of 6,688 genes of TPB using microarray revealed 6 esterase, 3 P450, and one glutathione S-transferase (GST) gene(s) that were significantly up-regulated. Economic and ecological impacts of wide-scale adoption of Bt cotton and insecticide use on grower profits and perceived risks of bollworm (BW) damage are being measured. These impacts have potential influence on BW resistance evolution to insecticides and Bt toxins. Pyrethroid susceptibility estimates in BW across the cotton belt did not vary from those generated during the previous three years; however, pyrethroid susceptibility estimates over the last 4 years have generally decreased compared to estimates generated during the late 1990’s. No patterns of pyrethroid or Bt susceptibility were identified in BW collected from different cropping landscapes. BW genomic sequences (n=392) containing xenobiotic processing genes and insecticide targets were identified by sequencing a BCA library. Over 23,000 microsatellite markers were identified from the genome of the BW. Sequencing and assembly of the BW transcriptome were completed, and microarrays were developed for gene expression analysis. In soybeans, stink bug species were surveyed across the MS Delta to document temporal and spatial dynamics of stink bug populations. Late-instar stink bug nymphs (green, southern green, and redbanded) were approximately twice as tolerant as adults when tested against organophosphorus or pyrethroid insecticides. Early stage nymphs should be targeted for insecticidal control. Tracking wireworm populations in sweetpotato and corn is providing new information on the impact of these soil-inhabiting pests on sweetpotato damage and crop rotation influences. Preplant applications of chlothianidin, chlorpyrifos, and imidacloprid reduced sugarcane beetle damage to sweetpotato in a large field cage study. Chlorpyrifos applications had no effect on reniform nematode populations in a study with insecticides applied alone and in combination with potassium N-methyldithiocarbamate.